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Patellofemoral Joint Kinematics in Individuals with and without Patellofemoral Pain Syndrome
N.J. MacIntyre, PT, PhD1; N.A. Hill, MSc2; R.A. Fellows, MSc2; R.E. Ellis, PhD3; D.R. Wilson, DPhil4
1 School of Rehabilitation Therapy, 31 George Street, LD Acton Building, Room 222, Queen's University, Kingston, ON K7L 3N6, Canada
2 Department of Mechanical Engineering and Human Mobility Research Centre, Queen's University, Apps Wing, Doran 2, Kingston General Hospital, 76 Stuart Street, Kingston, ON K7L 2V7, Canada
3 Surgical Planning Laboratory, Department of Radiology, Room ASBI, L1-050, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115
4 Department of Orthopaedics, University of British Columbia and Vancouver Coastal Health Research Institute, 910 West 10th Avenue, Room 3114, Vancouver, BC V5Z 4E3, Canada
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A commentary is available with the electronic versions of this article, on our web site (www.jbjs.org) and on our quarterly CD-ROM (call our subscription department, at 781-449-9780, to order the CD-ROM).
In support of their research for or preparation of this manuscript, one or more of the authors received grants or outside funding from the Canadian Institutes of Health Research (CIHR MOP43883), the Natural Sciences and Engineering Research Council of Canada (Strategic Grant), the Ontario Centres of Excellence, the Ontario Research Fund, the Physiotherapy Foundation of Canada (AMMFOP), the Arthritis Society/Canadian Institutes of Health Research (research fellowship for N.J.MacI.), and the Canadian Arthritis Network (scholarship for D.R.W.). None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Investigation performed at the Human Mobility Research Centre, Queen's University and Kingston General Hospital, Kingston, Ontario, Canada

The Journal of Bone and Joint Surgery, Incorporated
J Bone Joint Surg Am, 2006 Dec 01;88(12):2596-2605. doi: 10.2106/JBJS.E.00674
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Background: Patellofemoral pain syndrome is a prevalent condition in young people. While it is widely believed that abnormal patellar tracking plays a role in the development of patellofemoral pain syndrome, this link has not been established. The purpose of this cross-sectional case-control study was to test the hypothesis that patterns of patellar spin, tilt, and lateral translation make it possible to distinguish individuals with patellofemoral pain syndrome and clinical evidence of patellar malalignment from those with patellofemoral pain syndrome and no clinical evidence of malalignment and from individuals with no knee problems.

Methods: Three-dimensional patellofemoral joint kinematics in one knee of each of sixty volunteers (twenty in each group described above) were assessed with use of a new, validated magnetic resonance imaging-based method. Static low-resolution scans of the loaded knee were acquired at five different angles of knee flexion (ranging between —4° and 60°). High-resolution geometric models of the patella, femur, and tibia and associated coordinate axes were registered to the bone positions on the low-resolution scans to determine the patellar motion as a function of knee flexion angle. Hierarchical modeling was used to identify group differences in patterns of patellar spin, tilt, and lateral translation.

Results: No differences in the overall pattern of patellar motion were observed among groups (p > 0.08 for all global maximum likelihood ratio tests). Features of patellar spin and tilt patterns varied greatly between subjects across all three groups, and no significant group differences were detected. At 19° of knee flexion, the patellae in the group with patellofemoral pain and clinical evidence of malalignment were positioned an average of 2.25 mm more laterally than the patellae in the control group, and this difference was marginally significant (p = 0.049). Other features of the pattern of lateral translation did not differ, and large overlaps in values were observed across all groups.

Conclusions: It cannot be determined from our cross-sectional study whether the more lateral position of the patella in the group with clinical evidence of malalignment preceded or followed the onset of symptoms. It is clear from the data that an individual with patellofemoral pain syndrome cannot be distinguished from a control subject by examining patterns of spin, tilt, or lateral translation of the patella, even when clinical evidence of mechanical abnormality was observed.

Clinical Relevance: Since most patients with patellofemoral pain syndrome did not demonstrate abnormalities in patellar tracking during loaded knee flexion, other causative mechanisms must be explored to develop effective diagnostic and treatment strategies for this common musculoskeletal condition.

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    Norma J. MacIntyre, PT, Ph.D.
    Posted on January 10, 2007
    Dr. MacIntyre and Dr. Wilson respond to Dr. Grelsamer
    School of Rehabilitation Science, McMaster University, Hamilton, ON CANADA

    We thank Dr. Grelsamer for his interest in our study(1) and for this opportunity to clarify our work.

    While we agree with Dr. Grelsamer’s concern that the term ‘patellofemoral syndrome’ is problematic, the term remains widely used and, more importantly, is generally well defined by researchers who use it. A search of the term ‘patellofemoral pain syndrome’ in MEDLINE, CINHAL, and AMED databases yielded 40 articles published in 2006. Among these were 4 Cochrane Reviews of the numerous primary articles describing specific treatments for ‘patellofemoral pain syndrome’(2-5). It appears that the authors using this term recognize the limitations inherent in its use and address this by clearly defining the characteristics of their patient populations as we have done in our paper(1).

    We would like to emphasize that we identified participants with patellofemoral joint pain who, under current best clinical practice, would be referred for conservative treatment. We aimed to identify the subgroup of patients for whom treatment would focus on improving patellar tracking by using a battery of clinical tests to assess patellar alignment and dynamic patellar motion. Currently when other specific causes of patellofemoral joint pain cannot be identified, the assumption underlying treatment is that altered mechanics plays a causative role in many cases (even though evidence for this is not extensive). In the subgroup with patellofemoral pain and clinically observed malalignment (PFPS+mal), the MRI-based measures of patellar motion revealed that the patella was positioned slightly more laterally as the patella enters the trochlear groove. However, on an individual level, large overlaps in values were observed in comparison with the subjects in the other two groups. We conclude that “Our findings do not support the use of patellar tracking or alignment as an indicator of normal or abnormal joint function.” We don’t see a major inconsistency in stating that the pathogenesis of patellofemoral pain syndrome is not clearly understood and that our results are consistent with current understanding because our findings add to the evidence that patellar maltracking is not a clinically significant factor for most individuals with patellofemoral joint pain.

    The results of the clinical tests performed in our screening assessment would direct the focus of that treatment. Specifically, patients who tested positive for iliotibial band tightness or on the Hughston’s plica test were excluded. We chose to exclude these conditions since the extensor mechanism and patellofemoral joint pain would not be the primary focus of treatment. Conservative treatment for patients who test positively on the McConnell patellar glide test would involve taping, bracing or exercises based on the principle that positioning the patella more medially reduces pain. Similarly, observed malalignment of the lower limb or ‘catching’ of the patella on the squat test would direct treatment towards improving the lower limb biomechanics during functional activities. Therefore, participants with positive results for these tests were assigned to the PFPS+mal group. We wish to correct the description of our use of the patellar tracking (compression) test that is given in our manuscript. As summarized in Table 1 in our paper, 11 symptomatic patients with clinical evidence of malalignment and 5 symptomatic patients with no clinical evidence of malalignment tested positively(1). This test result was only used to assign recruits to either one of the symptomatic groups or to the control group. We agree that a positive test result only confirms patellofemoral joint pain and does not provide information regarding alignment of the patella.

    Our results do not support Dr. Grelsamer’s interpretation that only 5 subjects in our PFPS+mal group were “likely to exhibit malalignment on physical examination.” We did not specifically explore the relationships between clinical test results and associated kinematic measures because this was not the primary objective of the study and, as such, it was not appropriately powered to address this objective. A re-examination of our data shows that the individual values for lateral translation for the 5 patients Dr. Grelsamer identified as “likely to exhibit malalignment” (Figure 1, red symbols) are not obviously different from the values for the other 15 subjects included in this group (Figure 1, black symbols). It is clear that the results for these individuals are very close to the mean values for the entire PFPS+mal group and have not skewed the observations for lateral translation. Data from recruits testing positive on other clinical tests used to detect problems with patellar alignment and dynamic motion also contributed to the finding that the patella is positioned slightly more laterally in this symptomatic group. This additional analysis supports our position that Dr. Grelsamer’s concern that only 25% of our PFPS+mal group had clinical malalignment is unfounded. We believe that the group definitions used in our study are clinically relevant and our results provide important evidence to guide decision making in the conservative treatment of patients with patellofemoral joint pain.

    Fig. 1. Individual values for lateral patellar translation as a function of loaded knee flexion angle in the PFPS+mal Group. Red circles: 4 subjects with positive patellar tilt test. Red triangles: 1 subject with positive apprehension test.


    1. MacIntyre NJ, Hill NA, Fellows RA, Ellis RE, Wilson DR. Patellofemoral joint kinematics in individuals with and without patellofemoral pain syndrome. J Bone Joint Surg Am 2006;88:2596-2605.

    2. Heintjes E, Berger MY, Bierma-Zeinstra SMA, Bernsen RMD, Verhaar JAN, Koes BW. Pharmacotherapy for patellofemoral pain syndrome. The Cochrane Library. 2006;4:CD003470.

    3. Heintjes E, Berger MY, Bierma-Zeinstra SMA, Bernsen RMD, Verhaar JAN, Koes BW. Exercise therapy for patellofemoral pain syndrome. The Cochrane Library. 2006;4:CD003472.

    4. D’hondt NE, Struijs PAA, Kerkhoffs GMM, Verheul C, Lysens R, Aufdemkampe G, Van Dijk CN. Orthotic devices for treating patellofemoral pain syndrome. The Cochrane Library. 2006;4:CD002267.

    5. Brosseau L, Casimiro L, Robinson V, Milne S, Shea B, Judd M, Wells G, Tugwell P. Therapeutic ultrasound for treating patellofemoral pain syndrome. The Cochrane Library. 2006;4:CD003375.

    Ronald P Grelsamer, M.D.
    Posted on December 19, 2006
    There Is No "Patellofemoral Pain" Syndrome
    Mount Sinai Medical School, New York, NY

    To The Editor:

    I have two major concerns regarding the recent article by MacIntyre, et al.(1). The first is that the authors discuss kinematics in patients with “patellofemoral syndrome”, a syndrome that has never existed even though the term has been commonly used. Banishment of this term is one of the very few things that all members of the International Patellofemoral Study Group have agreed upon from the inception of this group in 1995(2,3). A medical syndrome is associated with a well-defined set of signs, symptoms, laboratory values, imaging studies and so forth. There is no such set of parameters associated with the “patellofemoral syndrome”. Patients who might at one time have been diagnosed with patellofemoral syndrome are now recognized to, in fact, suffer from a wide variety of completely unrelated conditions. A diagnosis by exclusion (i.e. “I do not understand why you have pain”) does not constitute a syndrome. Yet this seems to be the authors’ main criterion when they state that “The diagnosis is based on the clinical history [what history specifically denotes a patellofemoral syndrome?] and the exclusion of other causes of anterior knee pain.”

    Are saphenous nerve neuromas, tight iliotibial bands, core deficiencies and plicas part of the patellofemoral syndrome or are they in the “other causes”? If they are part of the “other causes” why are the various forms of malalignment singled out as being part of the patellofemoral syndrome and not also part of the “other causes”? If, on the other hand, they are all included under the umbrella of the “patellofemoral syndrome”, how can we expect any common thread among them other than pain? Thus, it is not clear to me how the authors can state that “Most of our kinematic findings are consistent with the accepted understanding of the etiology of patellofemoral pain syndrome” when they also state that the patellofemoral syndrome is “poorly understood”.

    My second major concern is that the authors allegedly looked at 20 military recruits with patella malalignment and compared them to 40 recruits without malalignment. On further inspection, however, only 5 patients were likely to exhibit malalignment on the physical examination--4 patients with a positive patellar tilt test and the one patient with a positive apprehension sign. The others had a positive glide test (relief of pain with medial displacement), compression test (pain with compression of the patella) and/or squat test (pain when performing a squat). These tests reflect irritation under and around the patella with or without chondral lesions, but none is an automatic reflection of malalignment.

    In the end, the authors examined 60 military recruits with anterior knee pain, 5 of whom demonstrated malalignment on physical examination. The fact that patients with and without malalignment exhibited similar kinematics can be easily explained by the fact that the authors added 15 subjects without malalignment to their “malalignment” pool.

    The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.


    1. MacIntyre, NJ, et al., Patellofemoral Joint Kinematics In Individuals with and without Patellofemoral Pain Syndrome. Journal Bone and Joint Surg Am 2006;88:2596-2605

    2. The International Patellofemoral Study Group, Grelsamer RP,: Patellofemoral semantics: the tower of Babel. 1997;Am J Knee Surg. 10 (2):92.

    3. Grelsamer RP: Patellar Nomenclature – The Tower of Babel Revisited. Symposium on patellofemoral arthroplasty. 2005;Clin Orthop 436:60-65.

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